PSI - Issue 42

Hiroshi Nishiguchi et al. / Procedia Structural Integrity 42 (2022) 1442–1448 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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was again observed by infrared Raman spectroscopy. Hydrogen exposure was performed at 270 o C because the hydrogen diffusion coefficient of silicon at room temperature (Seager et al. 1988) is of the order of 10 -14 m 2 /s, which is an extremely low value for the entry of hydrogen into the material at room temperature. 3. Experimental results 3.1. Effect of hydrogen exposure on cracks propagations around the indentation Figure 1 shows the laser microscopy images of the indentation and the cracks initiated at the corners of the indentation before and after the exposures to hydrogen gas at a high pressure of 100 MPa. Two indentation forces were employed: Figs. 1(a) and (b) present the images for a force of 0.98 N, while Figs. 1(c) and (d) present the images for

Fig.1 Vickers indentations and cracks.

Fig.2 Magnified views of the cracks in Fig.1.